External Firewire 80gb Drive


I am currently trying to create a movie in imovie of a family trip...it's about 40 minutes long and all i have left to do is edit sound and add a soundtrack. I recently updated to 10.4 and ilife 05 and went to work on the project which is stored in a Lacie external firewire 40gb hard drive with 25 gb of free space (it was previously used on mac 0S9 a couple of years ago)....it took a really long time to open and now takes forever to respond to a simple task of clicking from one clip to another. i don't think its a memory deal- i have 25gb free space on my computer itself and 35 free on the external hard drive...i posted this on the apple help support site and someone said that i might have to partition the external drive or something like that...am very confused and would appreciate any help! thank you in advance!